On Wednesday, a day before his final one at the Pentagon, U.S. Defense Secretary Robert Gates issued a statement of farewell to all U.S. military, the New York Post reported.

Your dedication, courage, and skill have kept America safe even while bringing the war in Iraq to a successful conclusion and, I believe, at last turning the tide in Afghanistan. Your countrymen owe you their freedom and their security, Gates wrote, adding that serving as Secretary of Defense for more than four years has been the greatest honor of my life.

I have signed the orders deploying you, all too often into harm's way. This has weighed on me every day. I have known about your hardship, your difficulties, your sacrifice, more than you can possibly imagine. I have felt personally responsible for each of you, Gates said.

You are the best that America has to offer. My admiration and affection for you is without limit, and I will think about you and your families and pray for you every day for the rest of my life, he added.

Gates, 67, was named Defense Secretary by President George W. Bush in 2006 and agreed to remain secretary after a request by President Barack Obama when he took office in 2009. Gates will be succeeded by CIA Director Leon Panetta.